Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, e.g., light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The structure of semiconductor material allows the material's electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed operations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, i.e., front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly, can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
One approach to achieving the objective of smaller, thinner semiconductor devices is to focus on eWLB technology. A one redistribution layer embedded wafer-level ball grid array package (1 L eWLB) provides a small, thin semiconductor device that has a high input/output (I/O) count and can incorporate semiconductor die having a high routing density. In a 1 L eWLB, an encapsulant is formed around a semiconductor die and one redistribution layer (RDL) is formed over the encapsulant and semiconductor die for electrical interconnect. The RDL serves as an intermediate layer for electrical interconnect within the semiconductor device including electrical interconnect between the semiconductor die within the device and points external to the device. Forming a single RDL increases the I/O count of the semiconductor device, while maintaining a thin package profile. However, in a 1 L eWLB, the power, signal, and ground traces are all designed within the single RDL, as opposed to spread over multiple RDLs. Forming the power, signal, and ground networks in a single RDL, eliminates the option of dedicating entire layers to providing power and ground planes. Without dedicated power and ground planes, routing design options are limited as power and ground traces need to be routed across the entire device to form an effective ground network and power distribution network (PDN). Forming ground and power networks within the single RDL consumes valuable real estate within the RDL and limits the space available for signal traces. In addition, without a dedicated ground plane layer electrostatic discharge (ESD) protection within the device is decreased. Finally, because a 1 L eWLB has only the one conductive layer, i.e., RDL, microstrip lines and decoupling capacitors cannot be formed within the device.